Panel-Insert Assembly and Method

ABSTRACT

A panel-insert assembly including a panel having a core and a skin layer positioned over the core, wherein the skin layer defines an opening therein, and an insert positioned below the skin layer, wherein the insert is aligned with the opening.

FIELD

This application relates to sandwich panels and, more particularly, tosandwich panels having an insert, such as a threaded insert, connectedthereto.

BACKGROUND

Sandwich panels are typically formed from a core sandwiched between twoface sheets. The core may be relatively thick, yet lightweight, ascompared to the face sheets. The face sheets may be relative thin, yetstiff. Therefore, sandwich panels typically possess relatively highstrength and stiffness at relatively low weight. As such, sandwichpanels are used in various applications, including aerospaceapplications, automotive applications, residential and commercialbuilding applications and the like.

For example, sandwich panels are used in the construction of aircraft,such as commercial aircraft. Specifically, sandwich panels are used asthe flooring, walls and bulkheads that define the passenger cabin of anaircraft. Therefore, such sandwich panels often are connected to theairframe of the aircraft such that loads applied to the sandwich panelsare transferred to the airframe.

Connecting a sandwich panel to an airframe is typically effected withmechanical fasteners, such as bolts, that engage threaded insertsconnected to the sandwich panel. The threaded inserts are typicallypotted (with an adhesive) into appropriately sized holes formed in thesandwich panel. The adhesives commonly used require long cure times, addundesired weight, and offer only limited pull strength protection sincethe load is transferred to the panel only through the adhesive. Also,care must be taken such that the threaded inserts are not placed toohigh in the holes, which may result in a gap being formed, or placed toolow in the holes, which may result in unintentional pullout duringtightening of the mechanical fastener.

Accordingly, those skilled in the art continue with research anddevelopment efforts in the field of sandwich panels.

SUMMARY

In one embodiment, the disclosed panel-insert assembly may include apanel having a core and a skin layer positioned over the core, whereinthe skin layer defines an opening therein, and an insert positionedbelow the skin layer, wherein the insert is aligned with the opening.

In another embodiment, the disclosed panel-insert assembly may include asandwich panel and an insert. The sandwich panel may include a corehaving a first major side and a second major side opposed from the firstmajor side, a first skin layer positioned over the first major side,wherein the first skin layer defines an opening, and wherein the openingis elongated along an opening axis, and a second skin layer positionedover the second major side. The insert may be positioned below the skinlayer, wherein the insert defines a threaded bore, and wherein thethreaded bore is aligned with the opening.

In another embodiment, disclosed is a method for connecting an insert toa panel, the panel including a core and a skin layer, the methodincluding (1) forming an opening in the skin layer; (2) inserting theinsert through the opening such that the insert is positioned below theskin layer; and (3) rotating the insert relative to the opening.

Other embodiments of the disclosed panel-insert assembly and method willbecome apparent from the following detailed description, theaccompanying drawings and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of one embodiment of the disclosedpanel-insert assembly;

FIG. 2 is a cross-sectional view of the panel-insert assembly of FIG. 1;

FIG. 3 is a top plan view of the panel-insert assembly of FIG. 1;

FIG. 4 is a top plan view of the insert of the panel-insert assembly ofFIG. 1;

FIG. 5 is a side elevational view of the insert of FIG. 4;

FIG. 6 is a flow chart depicting one embodiment of the disclosed methodfor connecting a threaded insert to a sandwich panel;

FIG. 7 is a perspective view of the opening forming step of the methodshown in FIG. 6;

FIG. 8 is one perspective view of the inserting step of the method shownin FIG. 6;

FIG. 9 is another perspective view of the inserting step of the methodshown in FIG. 6;

FIG. 10 is a perspective view of the aligning and rotating steps of themethod shown in FIG. 6;

FIG. 11 is flow diagram of an aircraft manufacturing and servicemethodology; and

FIG. 12 is a block diagram of an aircraft.

DETAILED DESCRIPTION

Referring to FIGS. 1-3, one embodiment of the disclosed panel-insertassembly, generally designated 10, may include a sandwich panel 12 andan insert 14. The insert 14 may be inserted through an opening 16 in thesandwich panel 12 in a manner that provides 360 degrees of contactbetween the insert 14 and the sandwich panel 12, thereby providing astrong connection therebetween.

As best shown in FIG. 2, the sandwich panel 12 may include a layeredstructure 13 that includes a core 18, a first skin layer 20 and a secondskin layer 22. The insert 14 may be positioned below the first skinlayer 20, thereby providing better load transfer between the insert 14and the sandwich panel 12 (as opposed to a potted insert).

While the layered structure 13 of the sandwich panel 12 is shown withthree layers 18, 20, 22, additional layers, such as additional corelayers, additional skin layers and/or additional other layers, may beincluded without departing from the scope of the present disclosure. Thesecond skin layer 22 may be optional and, therefore, may be omitted fromthe layered structure 13 of the sandwich panel 12 without departing fromthe scope of the present disclosure.

The core 18 of the sandwich panel 12 may include a first major side 24and an opposed second major side 26. The first skin layer 20 may beconnected (e.g., adhered, welded, braised, mechanically fastened etc.)to the first major side 24 of the core 18 and the second skin layer 22may be connected (e.g., adhered, welded, braised, mechanically fastenedetc.) to the second major side of the core 18, thereby sandwiching thecore 18 between the first skin layer 20 and the second skin layer 22.

The cross-sectional thickness T₁ of the core 18 of the sandwich panel 12may be relatively thick, as compared to the cross-sectional thicknessesT₂, T₃ of the first skin layer 20 and the second skin layer 22 (e.g.,T₁>T₂ and T₁>T₃). For example, the cross-sectional thickness T₁ of thecore 18 may be two or more times greater (e.g., five times greater) thanthe cross-sectional thickness T₂ of the first skin layer 20. However,the core 18 may have a relatively lower density (basis weight divided bycross-sectional thickness), as compared to the densities of the firstskin layer 20 and the second skin layer 22.

Structurally, the core 18 of the sandwich panel 12 may be solid.However, lower densities may be achieved using a non-solid structure. Asone specific, non-limiting example, the core 18 may be (or may include)a foam. As another specific, non-limiting example, the core 18 may befluted or may include fluting. As yet another specific, non-limitingexample, the core 18 may be (or may include) a honeycomb structure.

Compositionally, the core 18 may be formed from the same, similar ordifferent materials than the first 20 and second 22 skin layers.However, the core may typically be a structure with less density thanthe skin layers 20, 22. As one specific, non-limiting example, the core18 may be formed from a polymer (e.g., expanded polystyrene). As anotherspecific, non-limiting example, the core 18 may be a honeycomb structureformed from a composite, such as a carbon fiber-reinforced composite ora fiberglass composite. As yet another specific, non-limiting example,the core 18 may be a honeycomb structure formed from a ceramic or metal,such as titanium, steel, aluminum or an aluminum alloy.

The first skin layer 20, which may be single ply or multi-ply, may beany material capable of being layered over and connected to the core 18.As one specific, non-limiting example, the first skin layer 20 may be apolymer, such as a polymer film, sheet or mesh. As another specific,non-limiting example, the first skin layer 20 may be a composite, suchas a carbon fiber-reinforced composite or a fiberglass composite. Asanother specific, non-limiting example, the first skin layer 20 may be aceramic. As yet another specific, non-limiting example, the first skinlayer 20 may be a metal film, sheet or mesh.

The second skin layer 22, which may be single ply or multi-ply, may beformed from the same, similar or different material than the first skinlayer 20. As one specific, non-limiting example, the second skin layer22 may be a polymer, such as a polymer film, sheet or mesh. As anotherspecific, non-limiting example, the second skin layer 22 may be acomposite, such as a carbon fiber-reinforced composite or a fiberglasscomposite. As yet another specific, non-limiting example, the secondskin layer 22 may be a metal film, sheet or mesh.

In FIG. 1, only a portion of a sandwich panel 12 is shown. Those skilledin the art will appreciate that the overall size and shape of thesandwich panel 12 may depend on the end application. For example, thesandwich panel 12 may be used to construct the passenger cabin of anaircraft and, therefore, may be sized and shaped accordingly.Additionally, while the sandwich panel 12 is shown in FIGS. 1-3 as beinga substantially planar structure, non-planar sandwich panels 12 (e.g.,curved sandwich panels 12) are also contemplated.

Still referring to FIGS. 1-3, the opening 16 in the sandwich panel 12may be formed in the first skin layer 20. The opening 16 may extendthrough the cross-sectional thickness T₂ of the first skin layer 20.Therefore, the opening 16 may provide access to the core 18 positionedbelow the first skin layer 20. As is described in greater detail herein,the opening 16 may facilitate connecting the insert 14 to the sandwichpanel 12 by insertion of the insert 14 below the first skin layer 20 byway of the opening 16.

The opening 16 in the first skin layer 20 of the sandwich panel 12 mayhave a maximum length L and a maximum width W that allow the insert 14to pass therethrough. The width W of the opening 16 may be dictated bythe cross-sectional thickness T₄ (FIG. 5) of the insert 14. The length Lof the opening 16 may extend along an opening axis O, and may be greaterthan the width W (e.g., the opening 16 may be elongated), and the lengthL may be dictated by the major and minor dimensions D₁, D₂ of the insert14.

As best shown in FIGS. 1 and 3, the opening 16 in the first skin layer20 of the sandwich panel 12 may be obround in plan view. However,openings 16 of various shapes may be used without departing from thescope of the present disclosure. For example, while not shown in thedrawings, the opening 16 may be rectangular, trapezoidal, irregular orthe like.

The opening 16 in the first skin layer 20 of the sandwich panel 12 maybe formed using various techniques. As one non-limiting example, theopening 16 may be formed by cutting out, such as with a blade, a portionof the first skin layer 20. As another non-limiting example, the opening16 may be formed by machining, such as with a router, a portion of thefirst skin layer 20.

Referring to FIGS. 4 and 5, the insert 14 may include a body 30 havingan engagement surface 32 and an outer periphery 34. As best shown inFIG. 5, the engagement surface 32 of the body 30 of the insert 14 may besubstantially planar, thereby allowing the engagement surface 32 toflushly abut the first skin layer 20 when the insert 14 is inserted intothe sandwich panel 12 below the first skin layer 20, as shown in FIGS.1-3. However, those skilled in the art will appreciate that theengagement surface 32 of the body 30 of the insert 14 may beshaped/contoured (e.g., curved) to closely correspond with theshape/contour of the first skin layer 20 below which the insert 14 ispositioned.

Referring to FIG. 4, the body 30 of the insert 14 may include a majordimension D₁ extending along a major axis M₁ and a minor dimension D₂extending along a minor axis M₂, wherein the major dimension D₁ isgreater than the minor dimension D₂. For example, the major dimension D₁may be about 1.1 to about 3 times greater than the minor dimension D₂,such as about 1.5 to about 2 times greater than the minor dimension D₂.Furthermore, the major dimension D₁ may be greater than the length L ofthe opening 16 in the first skin layer 20, as shown in FIG. 3, while theminor dimension D₂ may be substantially equal to or less than the lengthL of the opening 16 in the first skin layer 20.

In one particular implementation, the major axis M₁ may be perpendicularto the minor axis M₂, as shown in the drawings with an ellipse-shaped(in plan view) insert 14. However, it is also contemplated that themajor axis M₁ may be transverse to, but not perpendicular to, the minoraxis M₂.

While an ellipse-shaped insert 14 is shown in the drawings, thoseskilled in the art will appreciate that inserts 14 of various shapes mayprovide the disclosed major and minor dimensions D₁, D₂, and may be usedwithout departing from the scope of the present disclosure. As onealternative example, the insert 14 may be a non-elliptical oval. Asanother alternative example, the insert 14 may be rectilinear (e.g., arectangle). As yet another alternative example, the insert 14 may havean irregular and/or non-symmetric shape.

The body 30 of the insert 14 may define a bore 36 therein. The bore 36may be sized and shaped to receive and engage a mechanical fastener,such as a screw, a bolt, a rivet or the like. In one particularimplementation, the bore 36 of the insert 14 may be threaded to receiveand engage a threaded fastener (e.g., a screw or a bolt).

Optionally, the portion of the body 30 surrounding the bore 36 may havea greater cross-sectional thickness T₄ than the rest of the body 30 toprovide the bore 36 with greater depth. For example, the body 30 of theinsert 14 may have a flanged or T-shaped profile, as shown in FIG. 5. Atthis point, those skilled in the art will appreciate that providing theinsert 14 with a deeper threaded bore 36 may facilitate a strongerconnection between the insert 14 and a threaded mechanical fastener.

The insert 14 may be formed from various materials or combination ofmaterials. As one general, non-limiting example, the insert 14 may beformed from metal, such as steel. As another general, non-limitingexample, the insert 14 may be formed from a polymer, such aspolyethylene terephthalate. As another general, non-limiting example,the insert 14 may be formed from a combination of materials, such as apolymer body having a metallic threaded insert (defining the bore 36)connected thereto. For example, the metallic threaded insert may bepress-fit into the polymer body. As yet another general, non-limitingexample, the insert 14 may be formed from a combination of materials,such as a ceramic body having a metallic threaded insert (defining thebore 36) connected thereto. For example, the metallic threaded insertmay be press-fit into the ceramic body. As one specific, non-limitingexample, the insert 14 may be a steel, such as a stainless steel, nutplate.

As shown in FIGS. 1-3, the insert 14 may be connected to the sandwichpanel 12 by inserting the insert 14 through the opening 16 in the firstskin layer 20 such that the insert 14 is positioned below the first skinlayer 20 (e.g., between the first skin layer 20 and the core 18). Oncebelow the first skin layer 20, the insert 14 may be oriented such thatthe entire outer periphery 34 of the insert 14 is positioned verticallybelow (relative to the vertical axis V of the insert 14 shown in FIG. 2)the first skin layer 20 and radially outside (relative to vertical axisV of the insert 14) of the opening 16 in the first skin layer 20,thereby providing 360 degrees of contact between the engagement surface32 of the insert 14 and the underside 21 of the first skin layer 20 ofthe sandwich panel 12.

Also disclosed is a method for connecting an insert to a sandwich panel.One embodiment of the disclosed method is shown in FIG. 6 and isgenerally designated 100. The method 100 is described below withreferences to FIGS. 7-10. Additional steps may be included in thedisclosed method 100 without departing from the scope of the presentdisclosure.

At Block 102, the method 100 may begin with the step of forming anopening 16 in the skin layer 20 of the sandwich panel 12, as shown inFIG. 7. The opening 16 may extend through the skin layer 20 (down to thecore 18), and may have a length L and a width W. The opening 16 may beformed by cutting, machining or the like the skin layer 20 of thesandwich panel 12.

At Block 104, the insert 14 may be inserted through the opening 16 inthe skin layer 20 of the sandwich panel 12, as shown in FIGS. 8 and 9.To facilitate insertion of the insert 14, the insert 14 may be arrangedsuch that the minor dimension D₂ of the insert 14 is aligned with thelength L (FIG. 7) of the opening 16, thereby allowing the smaller, minordimension D₂ of the insert 14 to pass through the opening 16.

The insert 14 may be inserted such that it is positioned below the skinlayer 20 of the sandwich panel 12. In one optional variation, a portionof the skin layer 20 may be delaminated from the core 18 to facilitatereceiving the insert 14 below the skin layer 20 (e.g., between the skinlayer 20 and the core 18). In another optional variation, a portion ofthe core 18 may be removed (e.g., cut out) to form a void sized andshaped to accommodate the insert 14.

At Block 106, the insert 14 (particularly the threaded bore 36 of theinsert) may be aligned with the opening 16 in the skin layer 20 of thesandwich panel 12, as shown in FIG. 10. For example, the insert 14 maydefine a bore 36, such as a threaded bore 36, and the bore 36 of theinsert 14 may be vertically aligned (see vertical axis V in FIG. 2) withthe opening 16 in the skin layer 20 of the sandwich panel 12.

At Block 108, the insert 14 may be rotated relative to the opening 16,as shown by arrow R in FIG. 10. The rotation may be made about thevertical axis V (see FIG. 2) such that the major dimension D₁ (see FIG.4) of the insert 14 is aligned with the length L (see FIG. 3) of theopening 16, thereby providing 360 degrees of contact between theengagement surface 32 (FIG. 4) of the insert 14 and the underside 21(FIG. 2) of the skin layer 20 of the sandwich panel 12. As one example,when the major axis M₁ is substantially perpendicular to the minor axisM₂, the rotating step (Block 108) may involve rotating the insert 14ninety degrees about the vertical axis V. As another example, therotating step may require rotating the insert 14 less than ninetydegrees (or more than ninety degrees), such as when the insert 14 isnonsymmetrical.

Thus, in the final, rotated configuration, the major axis M₁ (FIG. 4) ofthe insert 14 may be aligned with (e.g., substantially parallel with)the opening axis O (FIG. 3) of the opening 16 in the sandwich panel 12,as shown in FIG. 1.

Examples of the disclosure may be described in the context of anaircraft manufacturing and service method 200, as shown in FIG. 11, andan aircraft 202, as shown in FIG. 12. During pre-production, theaircraft manufacturing and service method 200 may include specificationand design 204 of the aircraft 202 and material procurement 206. Duringproduction, component/subassembly manufacturing 208 and systemintegration 210 of the aircraft 202 takes place. Thereafter, theaircraft 202 may go through certification and delivery 212 in order tobe placed in service 214. While in service by a customer, the aircraft202 is scheduled for routine maintenance and service 216, which may alsoinclude modification, reconfiguration, refurbishment and the like.

Each of the processes of method 200 may be performed or carried out by asystem integrator, a third party, and/or an operator (e.g., a customer).For the purposes of this description, a system integrator may includewithout limitation any number of aircraft manufacturers and major-systemsubcontractors; a third party may include without limitation any numberof venders, subcontractors, and suppliers; and an operator may be anairline, leasing company, military entity, service organization, and soon.

As shown in FIG. 12, the aircraft 202 produced by example method 200 mayinclude an airframe 218 with a plurality of systems 220 and an interior222. Examples of the plurality of systems 220 may include one or more ofa propulsion system 224, an electrical system 226, a hydraulic system228, and an environmental system 230. Any number of other systems may beincluded.

The disclosed panel-insert assembly 10 and method 100 may be employedduring any one or more of the stages of the aircraft manufacturing andservice method 200. For example, components or subassembliescorresponding to component/subassembly manufacturing 208, systemintegration 210, and or maintenance and service 216 may be fabricated ormanufactured using the disclosed panel-insert assembly 10 and method100. Also, one or more apparatus examples, method examples, or acombination thereof may be utilized during component/subassemblymanufacturing 208 and/or system integration 210, for example, bysubstantially expediting assembly of or reducing the cost of an aircraft202, such as the airframe 218 and/or the interior 222. Similarly, one ormore of system examples, method examples, or a combination thereof maybe utilized while the aircraft 202 is in service, for example andwithout limitation, to maintenance and service 216.

The disclosed system and method are described in the context of anaircraft; however, one of ordinary skill in the art will readilyrecognize that the disclosed service system may be utilized for avariety of different components for a variety of different types ofvehicles. For example, implementations of the embodiments describedherein may be implemented in any type of vehicle including, e.g.,helicopters, passenger ships, automobiles and the like.

Although various embodiments of the disclosed panel-insert assembly andmethod have been shown and described, modifications may occur to thoseskilled in the art upon reading the specification. The presentapplication includes such modifications and is limited only by the scopeof the claims.

What is claimed is:
 1. A panel-insert assembly comprising: a panelcomprising a core and a skin layer positioned over said core, whereinsaid skin layer defines an opening therein; and an insert positionedbelow said skin layer and aligned with said opening.
 2. The panel-insertassembly of claim 1 wherein said panel is a sandwich panel and furthercomprises a second skin layer, wherein said core is positioned betweensaid skin layer and said second skin layer.
 3. The panel-insert assemblyof claim 1 wherein said opening is elongated.
 4. The panel-insertassembly of claim 1 wherein said opening has a maximum length.
 5. Thepanel-insert assembly of claim 4 wherein said insert has a majordimension and a minor dimension, said minor dimension being less than orequal to said maximum length.
 6. The panel-insert assembly of claim 5wherein said major dimension is greater than said maximum length.
 7. Thepanel-insert assembly of claim 1 wherein said insert is positionedbetween said skin layer and said core.
 8. The panel-insert assembly ofclaim 1 wherein said insert defines a bore.
 9. The panel-insert assemblyof claim 8 wherein said bore is threaded.
 10. The panel-insert assemblyof claim 1 wherein said insert comprises a combination of materials. 11.A panel-insert assembly comprising: a sandwich panel comprising: a corehaving a first major side and a second major side opposed from saidfirst major side; a first skin layer positioned over said first majorside, wherein said first skin layer defines an opening, and wherein saidopening is elongated along an opening axis; and a second skin layerpositioned over said second major side; and an insert positioned belowsaid skin layer, wherein said insert defines a threaded bore, andwherein said threaded bore is aligned with said opening.
 12. Thepanel-insert assembly of claim 11: wherein said opening has a maximumlength, wherein said insert has a major dimension and a minor dimension,and wherein said minor dimension is less than or equal to said maximumlength.
 13. The panel-insert assembly of claim 12 wherein said majordimension is greater than said maximum length.
 14. The panel-insertassembly of claim 11 wherein said insert has a major dimension along amajor axis and a minor dimension along a minor axis, wherein said majordimension is greater than said minor dimension.
 15. The panel-insertassembly of claim 14 wherein said major axis is substantially parallelwith said opening axis.
 16. A method for connecting a threaded insert toa panel, said panel comprising a core and a skin layer, said methodcomprising: forming an opening in said skin layer; inserting saidthreaded insert through said opening such that said threaded insert ispositioned below said skin layer; and rotating said threaded insertrelative to said opening.
 17. The method of claim 16 further comprisingaligning said threaded insert with said opening.
 18. The method of claim16 wherein said forming said opening comprises elongating said openingalong an opening axis.
 19. The method of claim 18 wherein said rotatingcomprises rotating said insert until a major axis of said insert issubstantially parallel with said opening axis, wherein said insertcomprises a major dimension along said major axis and a minor dimensionalong a minor axis.
 20. The method of claim 19 wherein said insertingcomprises aligning said minor dimension with said opening.